1. Field of the Invention
The present invention relates generally to a communication apparatus and method of operation thereof and, more particularly, to a communication apparatus that comprises a set of interconnects in a chassis, embodied by a mid-plane, that achieves communication density and high availability goals by providing multiple types of redundancy along with the ability to add/remove modules without having to restart the system.
2. Background Description
Computer and communication systems typically use a multitude of modules (e.g., printed circuit boards with electrical components) that can be inserted into and extracted from a chassis to support a large number of interfaces. Without proper support, these modules cannot be dynamically added or removed because the insertion/removal corrupts a shared resource, such as power or a communication bus. Hence, high availability goals (service disruption measured in seconds per year) cannot generally be achieved.
To achieve high-availability, card redundancy is typically employed in order to allow services to be provided by one card while the other is being serviced either due to a fault or a capability upgrade. Card redundancy can be employed on either a central controlling card, interface modules, or both.
There are two types of redundancy: one-to-one (1:1) redundancy, and N-to-one (N:1) redundancy. 1:1 redundancy is characterized where there is a xe2x80x9cworkingxe2x80x9d (i.e., active) unit and a xe2x80x9cprotectionxe2x80x9d (i.e., standby) unit in a one to one relationship. If the working unit is removed from service, either due, for example, to a failure or a maintenance operation, then the protection unit takes over. N:1 redundancy is characterized where N units are working, and they are backed up by a single protection card. N:1 redundancy are typically more cost effective.
Interconnect is crucial to supporting redundancy because more than one card may have to be switched into and out of the service providing path. The external interface generally needs to be able to be driven from more than one card in order to achieve this switching function. Furthermore, if there are different interface types, then there needs to be a interconnect network for each interface type that operates with redundancy.
Also, to achieve high availability, faults have to be detected and isolated. One method for achieving isolation is to have separate circuits for each card. However, if these circuits are in the form of a multi-bit bus, then a large number of connector pins is used by central controlling card, which is not only costly, but can increase the probability of failure.
It is a feature and advantage of the present invention to provide a communication apparatus, embodied by a mid-plane, that achieves communication density and high availability goals by providing multiple types of redundancy along with the ability to add/remove modules without having to restart the system.
It is another feature and advantage of the present invention to allow modules to be dynamically added or removed to/from the midplane.
It is yet another feature and advantage of the present invention to provide a midplane apparatus that has an improved availability.
To achieve these features and advantages, the invention is an interconnect system that supports a combination of 1:1 system processor redundancy with redundant/isolated communication paths between them, 1:1 timing source redundancy, 1:1 high speed internal communication redundancy, and support for two or more N:1 redundant external interfaces. Lastly, to achieve density, high frequency communication is employed. High frequency communications requires careful routing and isolation techniques to ensure proper interference-free operation.
A chassis, in the form of a midplane design (i.e., the circuit modules plug in from both the front and the rear of the midplane), is used to hold equipment that provides communication services. In one embodiment, the midplane design enables cables to be attached to modules which, in turn, are secured to the back of the midplane. The rear modules preferably have a minimum of circuitry so as to render them the least likely to fail, and can be replaced in the event that they do fail. The front modules house the majority of the electronics. In operation, the rear modules route the interface signals to a card in the adjacent front slot, directly through the midplane. The design in accordance with the present invention advantageously enables the rear modules to stay in place while a front module is replaced for servicing. Thus, if a front module (i.e., interface electronics) needs to be replaced, the cables do not have to be detached and reattached to the rear module. Nor do the rear modules generally need to be detached from the midplane. The components and cables on the rear are thus rarely altered, with one obvious exception being the installation of new cables. Hence, servicing is generally performed from the front of the chassis.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Further, the purpose of the foregoing abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.